In recent years, various types of personal computers are widely popular such as the notebook type or desktop type. Further, of notebook type personal computers which can be driven by a battery, many of them are prepared with an external unit for feature expansion which is called docker (to be called as expansion unit). By preparing an expansion unit of this type, the notebook type personal computers achieve both portability (smaller in size and lighter in weight) and high performance at the same time, which are considered to be in the relationship of a tradeoff.
In many cases, the personal computers equipped with an expansion unit do not include a terminal which outputs a video signal to an external display. In other words, in many cases, a terminal for video signal output is provided on the side of expansion unit. In the case where an external display is used in such a personal computer, the video signal is output to the expansion unit via a connector provided for the connection with the expansion unit, and thus the video signal is output to the external display from the video signal output terminal of the expansion unit.
Here, let us suppose a case where an expansion unit is set in, for example, each of the office and at home. Further, let us suppose a case where, for example, the expansion unit set in the office is a new model, whereas the expansion unit set at home is an old-model, and the new-model expansion unit is provided with a terminal compliant with DisplayPort for outputting video signals, whereas the old-model expansion unit is provided with a terminal compliant with High-definition multimedia interface (HDMI) for outputting video signals. Further, it is supposed that the personal computer of the type which can support both of the old-model and new-model expansion units.
In the above-described case, when connecting the personal computer to the expansion unit set in the office, the port for outputting a video signal generated by the graphics processing unit (GPU) needs to be set as a video signal output port compliant with DisplayPort. On the other hand, when connected to the expansion unit set at home, the port for outputting a video signal generated by the GPU needs to be set as a video signal output port compliant with HDMI. The setting of the port is executed by loading either one of a video BIOS which sets up the port as a video signal output port compliant with HDMI and a video BIOS which sets up the port as a video signal output port compliant with DisplayPort. A video BIOS is one module in a system BIOS (basic input/output system) which executes an initialization process of the hardware.
In the meantime, it is general that personal computers of the recent model includes a power saving function which achieves the saving of power without degrading the operation efficiency of the user, which is called a suspend or a hibernation. With use of the energy saving function, the status at the time when an operation is paused is restored, and the operation is restarted continuously. The function of restoring the status at the time of immediately before a suspending or a hibernation is called resume.
Furthermore, personal computers of the recent model includes a function of being capable of attaching or detaching an external device while the power is on, which is called a plug and play.
In other words, the detaching or attaching of an expansion unit is not always carried out while the power of the personal computer is off (except for the power off state by suspend or hibernation), but it can be carried out while, for example, the power is on. The attachment of an external device while the power is on is called hot dock, whereas the detachment of an external device while the power is on is called hot undock.
Even with the above-described set-up, in the case where a personal computer separated from the expansion unit set in the office is to be connected to the expansion unit set at home, or reversely, a personal computer separated from the expansion unit set at home is to be connected to the expansion unit set in the office, the setting of the port for outputting video signals generated by the GPU must be altered, and therefore when the power of the personal computer is on, the computer needs to be restarted (reactivated) in order to reload the video BIOS.
As described above, in the case where the personal computer is attached to detached to only the expansion unit set in the office, or the personal computer is attached to detached to only the expansion unit set at hole, the restarting of the personal computer is not necessary. On the other hand, the restarting of the personal computer is required when it is re-connected between the expansion units set in the office and at home. In such operation circumstances, the user feels it troublesome to operate the computer.